The present invention relates to cryptography and, more specifically, to a system for encrypting and decrypting digital data using one or more equally weighted variable-length keywords.
Cryptography may be used to provide secure communication or storage of digital data such as voice, facsimile (FAX), electronic mail, credit card information, and television. Practitioners in the art have developed encryption algorithms, such as the Data Encryption Standard (DES). These algorithms require a user to enter a keyword to either encrypt or decrypt the data. Data encrypted using a given keyword can only be decrypted by using the same keyword. DES requires that the keyword be exactly six alphanumeric characters in length. The essence of the DES algorithm is a complex decision tree that alters the states of data bits in response not only to the key but also to the results of logical operations that it performs on groups of data bits. Encryption or decryption is very slow because these calculations take a large amount of time and must be performed sequentially.
Analog cryptographic systems are used to provide secure video transmissions over microwave links and cable television lines. These systems must operate at high speeds to accommodate video bandwidths.
It would be desirable to provide a cryptographic system that does not restrict the user's choice of key length and that operates fast enough to be used in real-time video and voice environments. These problems and deficiencies are clearly felt in the art and are solved by the present invention in the manner described below.